
int isHollow(int* a, int len) 
{ // voi 7 phan tu thi len/2 = 3; mang bat dau tu 0,
		

		int first, middle, count=0;
		int last = len;
		for (first = 0; first < len / 2; first++) {
			last = last - 1;
			if (a[first] == 0 || a[last] == 0) {
				break;
			}
		}
		for (middle = first; middle <= last; middle++) {
			if (a[middle]==0) {
				count++;
			} 
			if (a[middle] != 0) {
				return 0;
			}
		}
		if (count<3) return 0;
		return 1;
}

